* ThreadLocal is usually implemented with a WeakReference, which can have negative performance
   * properties; for example, calling WeakReference.get() on Android will block during an
   * otherwise-concurrent GC cycle.
   */
  private static final class TaskNonReentrantExecutor extends AtomicReference<RunningState>
      implements Executor, Runnable {

    /**

      if (!readable) return null
      if (!civilizedFileSystem && (currentEditor != null || zombie)) return null

      val sources = mutableListOf<Source>()
      val lengths = this.lengths.clone() // Defensive copy since these can be zeroed out.
      try {
        for (i in 0 until valueCount) {
          sources += newSource(i)
        }
        return Snapshot(key, sequenceNumber, sources, lengths)

    is a view of what created it, we use _as_.
 *  Fix: Permit response codes of zero for compatibility with OkHttp 3.x.
 *  Fix: Change the return type of `MockWebServer.takeRequest()` to be nullable.
 *  Fix: Make `Call.clone()` public to Kotlin callers.


## Version 4.0.0-RC1

_2019-06-03_

 *  First stable preview of OkHttp 4.


## Version 3.x

[Change log](https://square.github.io/okhttp/changelog_3x/)

    //     (All indices taken mod n.) If d and n are mutually prime, all elements will have been
    //     moved at that point. Otherwise, we can rotate the cycle a[1], a[1 + d], a[1 + 2d], etc,
    //     then a[2] etc, and so on until we have rotated all elements. There are gcd(d, n) cycles
    //     in all.

     *     under {@code directory}
     * @param currentPath canonical files already visited in the current directory tree path, for
     *     cycle elimination
     */
    private void scanDirectory(
        File directory,
        String packagePrefix,
        Set<File> currentPath,
        ImmutableSet.Builder<ResourceInfo> builder)

    }

    @Override
    public int invoke(R invokerRequest) throws InvokerException {
        requireNonNull(invokerRequest);

        Properties oldProps = (Properties) System.getProperties().clone();
        ClassLoader oldCL = Thread.currentThread().getContextClassLoader();
        try (C context = createContext(invokerRequest)) {
            try {
                if (context.currentThreadContextClassLoader != null) {

  } else {\n        this.switchTab(`#${navId}`)\n      }\n    }\n\n    this.onTabCreated($(`#${navId}`))\n  }\n\n  openTabSidebar(item, autoOpen = this._config.autoShowNewTab) {\n    let $item = $(item).clone()\n    if ($item.attr('href') === undefined) {\n      $item = $(item).parent('a').clone()\n    }\n\n    $item.find('.right, .search-path').remove()\n    let title = $item.find('p').text()\n    if (title === '') {\n      title = $item.text()\n    }\n\n    const link = $item.attr('href')\n   ...

         .add("*.publicobject.com", "sha1/T5x9IXmcrQ7YuQxXnxoCmeeQ84c=")
         .build());
    ```

 *  **Interceptors lists are now deep-copied by `OkHttpClient.clone()`.**
    Previously clones shared interceptors, which made it difficult to customize
    the interceptors on a request-by-request basis.

 *  New: `Headers.toMultimap()`.

        this.targetHost = targetHost;
        this.transport = transport.acquire();
        this.trees = new ArrayList<>();
        this.credentials = tf.getCredentials().unwrap(CredentialsInternal.class).clone();
    }


    /**
     * @return the configuration used by this session
     */
    @Override
    public final Configuration getConfig () {
        return this.transportContext.getConfig();
    }

    public CharSource asCharSource(Charset charset) {
      checkNotNull(charset);
      return CharSource.empty();
    }

    @Override
    public byte[] read() {
      return bytes; // length is 0, no need to clone
    }

    @Override
    public String toString() {
      return "ByteSource.empty()";
    }
  }

  private static final class ConcatenatedByteSource extends ByteSource {